A problem related to radio receivers in small wireless communication devices is that the radio frequency (RF) components need to be miniaturized. However, miniaturization of RF components will typically result in RF components that have reduced performance, in terms of noise and RF interference performance etc., than RF components that are not miniaturized, for example components that are used in products such as radio base stations. Furthermore, RF components need to be cost effective and power efficient which sets additional performance challenges. Hence, in order to enable use of such reduced performance RF components while still maintaining good radio performance in radio receivers, improved interference cancellation is needed.
A non-linear RF component generates intermodulation interference signals from a signal which passes the RF component and the intermodulation products typically deteriorate signals received in the receiver. A commonly used parameter for characterizing intermodulation is the so-called third order intercept point. This parameter can be directly measured in the component itself and RF component manufacturers specify this value in data sheets that describe the RF component. The third order intermodulation is typically a dominant source of interference but 5th order, 7th order or any odd order intermodulation products may cause problems in signal reception. Also even order IM distortion may fall in to the received signal frequency in homodyne receivers.
It is therefore of interest to overcome intermodulation distortion which is generated by active components in a receiver, for example a receiver in a wireless communication device. The active components may include any of a low-noise amplifier (LNA), an automatic gain controller (AGC), a mixer, an analogue-to-digital converter (ADC) or any other active component which is a part of a signal chain of a radio receiver. Additionally it is also of interest to overcome passive intermodulation (PIM) of radio frequency filters, for example duplex filters, in devices having receivers and transmitters that utilize at least one common antenna, for example in a wireless communication device.
US patent application publication US 2012/0295558 describes dynamic cancellation of passive intermodulation interference. The method presented in US 2012/0295558 is requires a test signal that originates from a transmitter to be able to correct PIM interference. If the interference is generated in the receiver filters or any other receiver signal path component the solution based on US 2012/0295558 will not be applicable.